1. By a door to the crew’s quarters
On one sailing, my cabin was right across from the entrance to the crew’s quarters. And although these may have been the most polite, professional crew members I have ever met (I heard shockingly little discussion between them from my cabin, and zero humming, singing, or whistling, as is sometimes the case), they work around the clock, so that door opened and closed well after I climbed into bed.
2. Above mechanical equipment
Once, I sailed in the most forward cabin on a ship — right over the bow — and I was awakened at the crack of dawn every day by the construction-like noise of the anchor as arrived in port. That cabin — and others near equipment the crew use — may be designated by an unmarked white area on the deck plan, so when you see a space like that, call the cruise line for more information.
3. Near elevators or stairs
Light sleepers everywhere request rooms away from elevators in hotels. The same should be true on cruise ships, only more so since passengers sometimes gather there — say, on the way to meals, shows, or for disembarkation.
4. Next to an ice machine
This is another one that is a common request in hotels for noise-a-phobes like myself, and should be on ships. Important to note: Some ships hide the ice machines in internal crew-only spaces; others keep them available for self-service.
5. Beside a laundry room
Not all ships have public laundry facilities, but on those that do, you want to avoid hearing the washers and dryers from inside your cabin.